Stage recontact is Ares biggest performance threat

NASA has concluded that the first and upper stages of its Ares I crew launch vehicle could collide after separation and this problem's impact on the Ares' development has been given the highest risk rating by the US space agency, according to documents obtained by Flight International.

This so-called recontact problem could end an Ares I mission - possibly catastrophically - during ascent. Failure could come seconds after firing of the separation pyrotechnics, if the upper stage's J-2X engine does not provide enough power fast enough to stop it from slowing down and colliding with the first stage and its motor, which would still be providing residual thrust.

While the Ares I's first-stage oscillations and possible contact between the rocket and its mobile launcher platform during lift-off are problems that have received publicity, the stages' recontact issue has not been made public.

But NASA has given stage recontact the highest possible risk ranking for the Ares project's cost, schedule and safety in documents dated 28 October 2008. NASA was not available for comment.

NASA ranks risks in terms of likelihood and consequence in a matrix table where one is the lowest risk and five the highest risk. The consequences are broken down into the categories of safety, performance (of the rocket in this case), schedule (maintaining it) and project cost. The oscillation issue is ranked as five for likelihood because it is a known motor characteristic, but is now ranked zero for cost, schedule and safety.

The first and upper stage recontact is given a likelihood of two, but it is ranked a five for all four consequences because finding a solution to ensure it does not happen is a high risk for all the consequence categories.

Of the eight top problems for Ares, only mobile launcher platform contact comes close with three consequence category fives, while the J-2X's development has a five for schedule.